Electromagnetic device



Jim 23, 1947. c; R. MASON ErAL n 2,414,961

amm DEVICE Filed ct. 1944 Pig. Z.

z4 g, 7l' Il 22 23 ffm will a lnve'ntes:

Charles R. Maso, Lawrence A. Burton |"he1'` Attorney.

Patented Jan.v 28,* 1947 Charles R. Mason,

Ballston Spa, Burton, Schenectady, N.

eral Electric Company,

Yor

and Lawrence A. Y., assgnors to Gena corporation of Newl Application October 26, 1944, SerialNo. 560,374

9 claims. (ci. zoo-111) Our invention relates to improvements in electromagnetic devices and more particularly to improvements in electromagnetically actuated circuit controlling devices such as contactors, relays and the like.

In electromagnetically actuated circuit controlling devices such as contactors, relays yand the like, wherein a movable rigid bridging contact is actuated under bias to engage rigid stationary contacts upon movement of an armature to the attracted position, the bridging contact tends to rebound when it strikes the stationary contacts. 'I'his tendency is accentuated if the armature is rigidly associated with the movable contact since the relatively heavy mass of the armature is added to that of the movable contact and the sudden stopping of both produces a greater reaction and, consequently, a greater tendency to rebound. The consequent bouncing of the parts causes arcing which not only produces needless wear of the contact surfaces, but also renders the circuit controlling action of the device uncertain. Such uncertainty of action cannot be tolerated in devices for use on warcraft and especially aircraft. Moreover, the bouncing action tends to produce general wear and misalignment, both of which result in unsatisfactory operation. It is usual in electromagnetically actuated circuit controlling devices such as contactors and the like to have the armature solidly engage its cooperating pole piece in the closed circuit position of the contacts. With such arrangements, it is necessary to make special provision not only to but also to compensate for contact wear or to and its cooperating pole piece. Such arrangements do not insure the maximum of contact pressure for a given attractive force or any increase in pressure as contact wear occurs. VAs far as We are aware, the arrangements heretofore proposed are complicated, costly and in general unsatisfactory when the devices are subject to shock and when space and factors as in aircraft.

An object of our invention is toprovide for electromagnetically actuated devices an improved contact and armature mounting which is re1a' tively simple, economical, light in weight and compact. Another objectof our invention is to u provide an improved contact and armature mounting which substantially eliminates rebound. A further object of our invention is to provide, in-an electromagnetically actuated circuit controlling device, an improved arrangement for maintaining a relatively high contact pressure with compensation for contact wear such as to 'insure even higher contact pressure as wear occurs. These and .other objects of our invention will appear in more detail hereinafter.

In accordance with our invention, we provide a relatively simple and compact armature and movable Contact mounting comprising two springs, one to bias the armature to the unattracted or circuit open position and the other to permit relative movement between the contacts and the armature after the contact has reached the closed circuit position during the movement of the armature to the attracted position. Also in accordance with our invention, We so arrange the parts of the electromagnetic device that in the circuit closed position of the armature there still remains a material air gap between the armature and its cooperating pole piece.

Our invention will be better understood from the following description when considered in connection with the accompanying sheet of drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Fig. 1 is-a plan view of an electromagnetically actuated switching device embodying our invention, with parts broken away; Fig. 2 is a vertical sectional elevation on the line 2 2 of Fig. 1, showing the device in the circuit open position; Fig. 3 is a part vertical sectional elevation on therline '3-3 of Fig. 1, showing the device in the circuit open position; Fig. 4 is similar to Fig. 3, showing the device in the circuit closed position; and Fig. 5 is an exploded perspective view illustrating parts of the contact mounting shown in the illustrated embodiment of our invention.

In the accompanying drawing,

As shown, this device comprises a shell l of suitable magnetic material within which is mounted an energizing winding 2 on a spool 3 of suitable nonmagnetic material. Within the shell l, there is an adjustably positioned pole piece 4 which, as shown, is threaded into the shell and held in position by a lock nut 5. Above the shell l, there magnetic material.

For controlling a circuit by the movement of 'ably conductively secured to terminals II. These terminals are secured to a base I2 of suitable insulating material by suitable means such as screws I3. This vrbase is fastened to the cap `5 of the magnetic structure by suitable means such as screws I4. For bridging the gap between the stationary contacts I0, there is provided a bridging ycontact I5 which is carried by the armature 9 transversely thereof. The bridging contact is provided with silver block inserts I6 which engage the contacts I when the armature 9 is moved to the attracted position.

In order to return the bridging contact I to the unattracted orv circuit open position, we provide a leaf biasing spring I1 carried by the armature transversely thereof and preferably at right angles to the bridging contact as shown. To provide abutments for the biasing spring I1 and also to prevent turning thereof, the ends of this spring are set in suitable notches I8 in the base I2. We have found that by tapering the biasing spring I1 as shown in Fig. 1 the bending stresses are more uniformly distributed throughout the spring than in a spring of uniform cross section. In consequence of this tapering, the effectivev life of the spring is increased without increasing the weight or space required by a sufficiently strong spring of different shape and having the same length of life as the tapered spring. In order to prevent turning of the biasing spring I1 relatively to the bridging contact I5, we provide guide means such as a saddle I9 having a pair of upward projections or flanges 20 between which the bridging contact is positioned and a pair of downward projections or ilangesZI which are at right angles to the flanges 20 and between which the biasing spring ispositioned.

In order to prevent rebound of the movable parts as the armature 9 moves to the attracted position, we provide, in accordance with our invention, an arrangement whereby the armature is tain the cushioning spring 22 in position under a predetermined initial strain as shown in Fig. 3.

In order to maintain in position under a predetermined initial bias or strain, as shown in Fig. 3, we provide means such as a cross bar 28 abutting thehead 21 ofthe screw 24` As shown, this bar is held in position under the heads of two diagonally opposite base screws I4. It will be apparent from Fig. 3 that, when the assembly screw 24 is seated tightly against the-saddle I9. the cushioning spring 22 is placed under a predetermined strain or bias to hold the bridging contact I5 in place between the anges 20 of the saddle I9.

In assembling the parts carried by the arma'- ture 9 at the upper end thereof, they are mounted in the order shown in Fig. 5, except for the lock washer 26, with the biasing contact I1 im-` mediately adjacent the armature. Just above the biasing spring I1 is anges 2| embracing the parallel side edges 29 of the biasing spring I1. Resting on the guide I9 between the flanges 20 thereof is the central portion of the bridging contact I5. Above this contact and resting on the, abutment faces 23 thereof is the circular cushioning spring 22. The foregoing parts are secured to the armature by the screw 24, which is threaded into the armature and screwed up tight against the lock washerl 26 on the saddle I9. The vshouldered portion 25 passes through clearance openings 30 and 3l` in the cushioning spring 22 and the contact I5, respectively. When the assembly of the armature 9, the contact I5 and the leaf springs I1 and 22 is completed, the cushioning spring 22 is stressed to take the configuration shown in Fig. 3. When the armature is mounted in the electromagnet and the bar 28 is set in the restraining position, the biasing spring I1 takes the configuration 0 shown in Fig. 2.

Upon energization of the winding 2 sufficiently to attract the armature 9 against the bias of the biasing spring I1, the armature starts toward the attracted position shown in Fig. 4. Until the free to move relatively to the bridging contact I5 45 bridging Contact l5* engages the stationary com following engagement thereof with the stationary contacts III. As shown, this arrangement comprises a cushioning `leaf spring 22 which is supported on suitable abutting surfaces 23 formed,

for example, by shaping thebridging contact I5 50 so that it is concave upward. For simplicity, the cushioning leaf spring 22 is preferably circular, as shown, since this eliminates the necessity for guides to nlaintain4 the spring in any particular alignment relativelyto the bridging contact.

In order to maintain the assembly of the cushioning leaf spring 22, the bridging contact I5,'the saddle I9, the biasing leaf spring I1 and the armature 9, we provide fastening or securing means such as a screw 24 which is threaded into the armature 9.v This screw has a shouldered portion 25 which seats ona lock washer 26 tightly against the guide I9 to hold the biasing spring I1 against the top of the armature 9. To permit some tilting of the contact I5 relatively to the direction of movement, of the armature 9 to and frornthe attractedposition, the shouldered portionw 25 of the screw. 24 projects through a clearance hole in the cushioning spring 22 and alsorthrough a clearance hole. in the bridging 70 in cbntact I5. Thisv provides some freedom of movement of thecontact I5 relatively to the stationary contacts I0 for better contact engagement. Above screw 24 has -an enlarged Vheadportion 21 to rethe shouldered portion 25, the

tacts III, the whole armature, contact and spring assembly moves as a unit against the bias of the leaf vspring I1. engages the stationary contacts I9, however, movement of the armature 9 and the bridging contact I5 as a unit ceases, but the armature 9 is free to travel a desired distance since the cushioning spring `22 yields to permit movement of the armature 9 relatively to the bridging contact I5. When the cushioning spring reaches the limit of its movement tobear against the central portion of the bridging contact as shown in Fig. 4, the travel of the Aarmature is completed, but there remains a desired air gap between the attracting surfaces of piece 4. With this air gap, the full attractive effort of the magnet is available to maintain relatively high contact pressure and there is no bat-v tering of the attracting surfaces. Also, the air gap insures compensation for such wear of the contact surfacesias may reasonably be expected. Furthermore, as contact wear occurs, the contact pressure is increased by virtue of the decrease the air gap. During the movement of the armature-9 between the -time when the bridging contact I5 engages the stationary contacts I0 and the position of the armature shown in Fig. 4, there isv no rebound of the bridging contact I5 since the armature has been free to travel toward the this armature assembly y the Saddle I9 with ltsA When the bridging contact I5 the armature and its pole i tion to bridge the abutments ilnal attracted position with the cushioning spring 22 absorbing the rebound forces.

' While we have shown and described our invention in considerable detail, we do not desire to be limited to the exact arrangement shown,

but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of our invention. l

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In an electromagnetically actuated device, an

turningv relatively thereto, means for guiding the ends of said biasing leaf spring 'to prevent turning of the armature, a contact carried by said armature and extending transversely thereof, said position arranged to allow some tilting of the contact relatively to said axis.

2. In an electromagnetically actuated device, an armature, a biasing leaf spring carried by said armature and extending transversely thereof, a movable contact carried by said armature and extending transversely thereof, said contact having spaced abutments on the side away from the armature, a cooperating stationary contact, a circular cushioning leaf spring carried by said armature in aposition to bridge the abutments on said contact deiiectable against said movable contact to limit the movement of the armature in the attracted direction after the movable contact engages the stationary contact whereby to limit the total movement of the armature to an amount materially less than the air gap between the armature and its attracting pole when the armature is in the unattracted position, and means for securing the springs and the contact to the armature arranged to allow some tilting of the movable contact relatively to the armature.

3. In an electromagnetically actuated device, a

plunger armature, a. biasing leaf spring carried by said armature and extending transversely thereof, a contact carried by said armature and extending transversely thereof, said contact having spaced abutments on the side away from the end of the armature, guide means for maintaining a predetermined angularity between said contact and said biasing spring, a circular cushioning leaf spring carried by said armature in a posion said contact, and means for securing the springs, the contact and the guide means to the armature with the contact tiltable relatively to the armature.

4. In an electromagnetically actuated circuit controlling device, an armature, a biasing leaf spring carried by said armature and extending transversely thereof, two spaced supports for said biasing spring mounted on opposite sides of the armature, a bridging contact carried by said armature and extending transversely thereof and havinga, concave outline on the side away from the armature, guide means for maintaining a predetermined angularity between said contact and said biasing spring, a cushioning leaf spring carried by said armature in a position to bridge the concavity of said contact, means forfsecuring said armature for 6 the springs, the contact and the guide means to the armaturejwith the contact tiltable relatively to the amature, and means for placing the biasing spring under a predetermined initial strain.

5. In an electromagnetically actuated circuit controlling device. a plunger armature, a biasing leaf spring mounted on one end of said armature and extending transversely thereof, two spaced supports for said biasing spring mounted on opposite sides of the armature, a bridging contact carried by said armature at one end thereof and having a concave outline on the side away from the armature, guide means for maintaining said wiping spring and said contact substantially perpendicular to each other, a. circular cushioning leaf spring carried by the end of said armature in a position to bridge the concavity of said c: n-v

tact, means for securing the springs, the contact and the guide means to the armature with the contact tiltable relatively to the armature, and means abuttlngsaid securing means for placing the biasing spring under a predetermined initial strain.

6. In an electromagnetically actuated circuit controlling device, a rectilinearly movable armature, means for moving the armature to the unattracted position comprising a biasing leaf spring carried by said armature and extending transversely thereof and spaced supports for said spring on opposite sides of the armature, two spaced stationary' contacts on opposite sides of said armature., a. cooperating bridging contact carried by said armature and extending trans-'- versely thereof, spaced raised portions on the side 35 of said bridging contact away from the armature, a cushioning leaf spring bridging the spaced portions of said bridging contact, fastening means engageable with said armature for securing the springs and the bridging contact to the armature with the bridging contact tiltable relatively to the armature, and stationary means engageable with said fastening means to place said biasing spring under a, predetermined initial strain when the armature is inthe unattracted position.

7. In an electromagnetically actuated circuit controlling device, a plunger armature, means for moving the armature to the unattracted position comprising a .biasing leaf spring carried by the armature and extending transversely thereof and spaced supports for said spring on opposite sides of the armature arranged to prevent turning of the spring, two spaced stationary contacts on opposite sides of said armature substantially from said supports, a cooperating bridging contact carried by said armature and extending transversely thereof, a saddle carried by maintaining the biasing spring and the bridging contact substantially perpendicular to each other, spaced raised portions on the side of said bridging contact away from the armature, a circular cushioning leaf spring bridging the raised portions on said bridging contact, a screw for securing the springs, the saddle and the bridging contact to the armature with the bridging contact movable relatively to the armature, a stationary member so positioned in contact with said screw and relatively to the supports of said biasing spring as to place the biasing spring under a predetermined strain when the armature is in the unattracted position.

8. In 4an electromagnetically actuated device, an amature, a pole piece, an energizing Winding for effecting movement of said armature from the unattracted position toward said pole piece, means for biasing the armatureaway from the stationary contact, 'a cooperating by the armature, a

pole piece, a movable contact carried resilient coupling between the armature and the movable contact deflectable to permit a predetermined movement of the amature relatively to the movable contact after the movable contact engages the stationary contact on movement of the armature toward the attracted position, and means for preventing further deflection of said resilient coupling whereby to prevent furtherA movement of the armature in the attracted direction, the construction and arrangement of parts y being such that the total movement of the armature from the unattracted position to the final position is materially less than the gap between the pole piece and the armature in the unattracted position.

9. In an electromagnetically actuated device, a plunger armature, a stationary pole piece, an energizing winding for effecting movement of the armature from the unattracted position toward said pole piece, a leaf spring carried by said armature transversely thereof forbiasing the armature away from said pole piece, two spaced stationary contacts, a cooperating rigid bridging contact carried by said armature transversely thereof at a predetermined angle to said biasing spring, a cushioning leaf spring freely supported b y said Contact at the edges thereof and connected to said armature at an intermediate point deflectable to permit a predetermined movement of the armature relativelyto the bridging contact after the bridging contact engages the stationary contacts on movement of the armature to the- 

